This invention relates generally to injection molding and more particularly to cooled thread split inserts used in injection molding bottle preforms of polyethylene terephthalate (PET).
Using a pair of thread split inserts in a mold to form the threaded neck portion of a PET bottle preform is well known as described and shown on a Project Report prepared by Unitech Engineered Products entitled "High Performance Preform Tool Set with Real-time Closed Loop Mold Monitoring". In addition to the threads, the neck portion of the preform has a circumferential ring collar which is also utilized in ejecting the preform from the mold. It is imperative that the neck portion of the preform be adequately cooled prior to ejection and thus the cooling rate of the neck portion is a major factor in determining minimum cycle time. As these preforms are molded in extremely large quantities, having a minimum molding cycle time is extremely critical to commercial viability. It has been found that the relatively slow cooling rate provided by existing thread split inserts is a major factor in preventing cycle time being reduced.